Justin Martyr — First Apology 61
As many as are persuaded and believe that what we teach and say is true, and who undertake to be able to live accordingly, are taught to pray and ask God with fasting for the forgiveness of their past sins, while we pray and fast with them.
Then they are brought by us to where there is water, and in the manner of regeneration by which we ourselves were regenerated they are regenerated. For in the name of God the Father and Master of all, and of our Savior Jesus Christ, and of the Holy Spirit, they then wash in the water.